Process and plant for handling thermoformed objects for a single-station thermoforming machine with form and cut mould

ABSTRACT

Process and plant for handling and stacking a plurality of thermoformed containers or lids, which comprises the following sequence of phases:  
     obtaining during a thermoforming phase mouldings of lids and containers, having at least three stacking protrusions or spacers, all having the same space arrangement in all the thermoformed products of the same moulding, at least one of the stacking protrusions or spacers of a same thermoformed object being set out in a non specular symmetric way with respect to at least a centre line of the respective container or lid and at a distance from the same centre line of the respective container or lid different from that of the others,  
     arranging one or a moulding of said containers or lids in at least one support template to keep them in order according to the spatial arrangement that they had during the thermoforming phase,  
     turning through a predetermined angle every other object or moulding of objects either containers or lids before or during their transfer to a stacking station, and  
     stacking mouldings of thermoformed containers or lids with alternate mouldings turned through said predetermined angle, so as to obtain stacks of containers or lids, where the stacking protrusions of a container or lid are offset with respect to those of the next container or lid in each stack.

BACKGROUND OF THE INVENTION

[0001] The present invention concerns a process and a plant for handlingthermoformed objects particularly for a single-station thermoformingmachine with form and cut mould.

[0002] In the thermoforming field of hollow packaging objects, and inparticular for objects of relatively low height and medium or largedimensions, such as lids or containers, for example round andrectangular plates, tubs and the like, it is becoming of crucialimportance for the manufacturer to be able to supply the market withthermoformed products, which have been correctly stacked, in perfectaxial arrangement and easily de-stackable or removable from the stack.This necessity is increasingly important as the growth of the automaticproduct packaging sector continues. This means that the stacks ofthermoformed products are usually destined to feed an automaticpackaging machine and, if the stacks have defects in their axialarrangement or the products in their stacks do not have a constant anduniform index between them, or one or more thermoformed products isstuck in the next or previous container in the stack, impeding or makingthe separation difficult, the packaging machine stops and needs anoperator to intervene, with consequent down time, increase of waste andthen packaging costs.

[0003] To resolve this problem and in a particular that one of thehollow thermoformed products' reciprocal sticking, it has already beensuggested to provide undercut recesses (b) in hollow thermoformedproducts (a) on the rim or on the wall or lateral walls (c) or on thebase (f) of the thermoformed products (see FIG. 1 of attached drawings),such recesses being obtained by providing corresponding fixed or mobileundercutting lugs or projections in the thermoforming mould.

[0004] However, if the recesses in the undercut recesses (b) on the sidewall or walls are too prominent, the extraction of the thermoformedproduct from the thermoformed mould becomes difficult; if, instead, theyare not very prominent, they are unable to prevent the stackedthermoformed products sticking to each other.

[0005] On the other hand, it is difficult, if not prohibitive, toconstantly and precisely check a certain number of parameters, namely:thickness, density, fluidity grade etc., of a sheet or belt ofthermoformable material in the mould of a thermoforming machine, andobtain therefore uniform and dimensionally perfect undercut recesses inthe thermoformed containers.

[0006] The recesses obtained with mobile projections in the mould arevery expensive to produce and to keep working efficiently. Experiencehas shown that the mobile projections in the mould frequently stopbecause of the inevitable dirtying due to the plastic material dustwhich always accrues in the form and cut mould of the thermoformingmachine.

[0007] In any case, then, it is known that in stacks of hollowthermoformed products (a) with vibrations and shaking during transportor warehouse handling, the undercutting recesses (b), if not perfect,cause the thermoformed containers or lids making up the single stacks tostick.

[0008] For all these reasons, instead of obtaining stacks axiallyaligned and with thermoformed products (a) kept distant a uniformdistance (d) as shown in FIG. 1, uneven stacks and with thermoformedproducts (a) arranged roughly and therefore not uniformly distanced fromone to the other (FIG. 2), in as much as the thermoformed products (a)are inevitably subject to sticking to each other, which makes separatingthem difficult, if not impossible, to de-stack or separate when used.Clearly, a stack of thermoformed products (a) not perfectly aligned inan axial direction and with products (a) that are difficult to de-stack,cannot be used in automatic distribution machines or in automaticfilling lines for thermoformed containers.

[0009] The same problems occur with the undercutting projections (b)when they are on the base (f) of thermoformed products, when theprojections often stick to each other with the result that the productstacks are defective, as shown in FIG. 3 of the drawings.

SUMMARY OF THE INVENTION

[0010] The main object of the present invention is to provide a processand a handling and stacking plant for a plurality of thermoformedobjects that can eliminate the difficulties mentioned above with thetechnical solutions mentioned above.

[0011] According to a first aspect of the present invention there isprovided a process for handling and stacking a plurality of thermoformedcontainers or lids, which is characterized in that it comprises thefollowing sequential phases:

[0012] obtaining during a thermoforming phase Mouldings of lids andcontainers, having at least three stacking protrusions or spacers, allhaving the same space arrangement in all the thermoformed products ofthe same moulding, at least one of the stacking protrusions or spacersof a same thermoformed object being set out in a non specular symmetricway with respect to at least a centre line of the respective containeror lid and at a distance from the same centre line of the respectivecontainer or lid different from that of the others,

[0013] arranging one or a moulding of said containers or lids in atleast one support template to keep them in order according to thespatial arrangement that they had during the thermoforming phase,

[0014] turning through a predetermined angle every other object ormoulding of objects either containers or lids before or during theirtransfer to a stacking station, and

[0015] stacking mouldings of thermoformed containers or lids withalternate mouldings turned through said predetermined angle, so as toobtain stacks of containers or lids, where the stacking protrusions of acontainer or lid are offset with respect to those of the next containeror lid in each stack.

[0016] According to another aspect of this invention there is provided aplant for handling and stacking thermoformed containers or lids havingat least three projections acting as stacking spacers, at least one ofwhich is arranged at non specular symmetry with respect to at least acentre line of the respective container or lid, said plant including, insequence, a receiving station for a container or lid or a moulding ofcontainers or lids, at least a stacking or working station for saidcontainers or lid, a stacking station for said containers or lids, meansof transferring the containers or lids from the receiving station to thestacking station through each working or handling station, and ischaracterized in that at least one of the said handling stationsincludes handling means arranged to rotate through a predetermined angleevery other moulding of containers or lids before or during theirtransfer to said stacking station, thereby obtaining stacks of lids orcontainers, where the stacking spacers of a container or lid areangularly offset with respect to those of the next container or lid.

[0017] Advantageously, the transfer devices include a step rotatingconveyer.

BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Further aspects and advantages of the present invention willbecome clearer in the following detailed description of some currentlypreferred embodiments of handling and stacking plants, given by way ofnon limiting examples with reference to the accompanying drawings, inwhich:

[0019]FIGS. 1 and 2 show a partial cross section view of a stack ofthermoformed products with stacking recesses on side walls according tothe prior art;

[0020]FIG. 3 show a partial view in cross section of a stack ofthermoformed products with undercutting recesses on the base of theproducts according to the prior art;

[0021]FIG. 4 is a schematic front view, slightly from above of ahandling and stacking plant according to the present invention installeddownstream of a single station thermoforming machine with form and cutmould;

[0022]FIG. 4a shows a detail of FIG. 4;

[0023]FIG. 4b shows a variant of FIG. 4, in which a thermoformed productis deposited, after having been partially turned, on a thermoformedobject that has not been turned;

[0024]FIG. 5 is a schematic front view of two containers, one on top ofthe other, and turned 180° one to the other before their reciprocalstacking;

[0025]FIGS. 6 and 7 show each a partial cross section of thermoformedobjects provided with stacking spacers on the base thereof and stackedaccording to the process of the present invention;

[0026]FIG. 8 is a is a partial cross section view of thermoformedobjects provided with stacking spacers on the rim thereof and stackedaccording to the process of the present invention;

[0027]FIG. 9 shows a container with an intermediate level arrangedbetween base and rim thereof and provided with stacking spacers:

[0028]FIG. 10 is a schematic front view, slightly from above, of asecond embodiment of the handling and stacking plant according to thepresent invention installed downstream of a single station thermoformingmachine with from and cut mould,

[0029]FIG. 11 shows a detail on an enlarged scale and a cross sectiontaken along the line XI-XI of FIG. 10;

[0030]FIG. 12 shows a schematic front view, slightly from above a thirdembodiment of a handling and stacking plant according to the presentinvention; and

[0031]FIG. 13 shows a variant of the plant in FIG. 12

[0032] In the accompanying drawings similar or same parts or componentshave been identified with the same reference numerals.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0033] With reference first to all FIGS. 4 to 9, it will be seen that aplant 1, according to the present invention, for handling and stackingthermoformed containers or lids (hereafter called thermoformed objectsor products) 2 comprises, in sequence, a station 3 for receiving orloading a moulding of products 2, a step conveyer 5, of the carouseltype, a handling station or handling device 6 downstream of thereceiving station 3 and designed to cause the alternate moulding ofproducts 2 to rotate through a predetermined angle, and a stackingstation 4 for containers and lids 2.

[0034] Each thermoformed product 2 (for example a rectangular tub, asshown in FIGS. 5 and 7 to 9 or a cup as shown in FIG. 6) is produced ina thermoforming machine or press 31 with form and cut mould 32 and withtwo couples 8 a and 8 b of stacking spacers or projections on the baseor the rim of the thermoformed product 2 or on a surrounding levelbetween base and rum. A couple of spacers 8 a are arranged at a distancefrom the transversal centre line m-m of the respective container 2 notspecularly symmetrical with respect to another couple 8 b, so that,thanks to the alternate rotation of the product mouldings 2 (as will befurther explained below), it is possible to obtain stacks 7 of products2, in which the couples of stacking spacers 8 a and 8 b of athermoformed product 2 are offset with respect to those of the productwhich follow it or precede in the stack (see FIGS. 5 to 9 in thedrawings).

[0035] The thermoforming press 31 has a lifting plate 30, for example ofthe suction type, which picks up the thermoformed products 2 from themould 32 of the thermoforming press 31 and deposits them on a templateframe 9 a-12 a of the rotating conveyer 5 positioned in the receivingstation 3.

[0036] The carousel conveyer 5 has, e.g. four spokes 9,10,11,12 all atright angles to each other, all terminating with their own respectivetemplate frame9 a, 10 a, 11 a and 12 a. The template frames are arrangedon the same plane and at the same distance from a vertical axis x-x ofcommon rotation, e.g. in the direction as indicated by an arrow A. Thefour spokes 9-12 are preferably integrated with a central plate 13, inturn supported and rotatable by a framework or central mounting 14, inwhich preferably there is an electric step motor 14 a for constant steprotation of the conveyer.

[0037] The handling station or handling device 6 comprises a supportstructure, an overhanging arm 15 having one end fixed to a fixed support16, while its other end supports a head or a real handling device 17which can rotate about a vertical axis and be raised and lowered. To beable to make the raising and lowering movements for the head 17, variousmethods can be adopted, e.g. in FIG. 4 the arm 15 is slidably mounted onthe support 16 along a couple of vertical guides 16 a and is controlledto carry out raising or lowering movements by a screw-nut thread group16 b and controlled by a reversible electric motor 16 c.

[0038] Handling device 17 on the free end of the arm 16 comprises e.g.an electric motor—gearbox unit 18 fixed with vertical axis through apassing opening in the arm 15, a plate 19 rotatable around a verticalaxis and supported underneath the motor-gear unit 18, and a multiplicityof tubular spacers 20 facing downwards and having their upper end fixedto the lower face off the turning plate 19, while their lower endsupports at their lower end a suction block. The reciprocal distancingof the blocks or suckers 21 is equal to homothetic to that of thereceiving openings of the thermoformed products 2 foreseen in eachtemplate or template frame 9 a-12 a, so that when the handling device islowered by the motor 16 c on a template, the blocks or suckers 21 go torest and engage the base of the thermoformed products 2 carried by thetemplates. Each block or sucker 21, through its spacer 20 and suitabletubing, e.g. in the turning plate 19, can be connected through pilotvalves, for example by a programmable command unit 25, with a vacuumsource (not shown in drawings) of any suitable type.

[0039] As illustrated in FIG. 4b, once the handling group 17 has removedthe thermoformed products 2 from a template 9 a-12 a and has carried outa predetermined angular movement, the turned thermoformed products 2 canbe positioned directly on the template from which they have been takenor on the template which follows immediately and is loaded withthermoformed products 2 which have not been turned.

[0040] The stacking station 4 can be of any suitable type, e.g. the typewith a lower platen 26 which supports a plurality of pushing devices 27,which push upwards from underneath the moulding of products 2 broughtfor example from the template frame 12 a once it has reached a correctposition above the platen 27, and an upper fixed platen 28 on whichstacks 7 of thermoformed products 2 are formed and stacked. Theresulting stacks 7 are formed by thermoformed objects 2, which havingbeen turned through 180° in alternate mouldings by the handling group17are stacked as shown in FIGS. 6 to 9 , i.e. with a couple of stackingprotrusions 8 a of one container arranged above, but offset so as not tointerfere with the couple of stacking protrusions 8 b of the lowercontainer. Thanks to this reciprocal misalignment of the stackingprotrusions, it is possible to completely avoid having the protrusions,and therefore the products 2, stick one inside the other, therebyconstantly obtaining stacks 7 of thermoformed products 2 always axiallyaligned and, therefore, always positioned perfectly even duringtransport and handling after stacking.

[0041]FIGS. 8 and 9 show in detail stacking protrusions 8 a and 8 b,which are provided in the flat rim or flange 2 a of each thermoformedproduct 2 or at a surrounding level 2 b positioned between the base andthe free rim of the containers 2.

[0042]FIG. 10 shows a variant of the embodiment shown in FIG. 4. In therotating conveyer 5 the arms or spokes from 9 to 12 terminate with arespective circular support frame, respectively 39, 40, 41 and 42,within which a respective template 9 a-12 a is supported and can berotated. In particular, each arm 9-12 supports at the circularsupporting frame (as better seen in FIG. 11) an electric motor 46 with avertical axis, on whose output shaft 46 a a pinion 44 is keyed whichmeshes with a circular rack or a length of circular rack 43 integral inrotation with the respective template, for example 9 a. The template 9 ais preferably rotatably supported on a respective template frame 39-42by at least three radial pins 9 b-12 b (only pin 9 b being visible inthe drawings) which are mounted on a respective ball bearing 9 c-12 cand guided by bearings 9 d-12 d on a vertical axis which roll on theinternal wall of the respective circular frame 39-42.

[0043] In use, during transfer from the receiving station 3 or duringthe stop at the handling station 6, the motor of the arm 9-12 concernedis energized by a program control unit 25, so as to cause a partialrotation, for example through 180°, of every other template 9 a-12 aloaded with thermoformed products 2, so as to obtain stacks 7 ofthermoformed products 2 at the stacking station 4, as shown in FIGS. 6to 9.

[0044] If desired, the handling device 7, after having caused a mouldingof thermoformed products 2 picked up from a template 9 a-12 a in thehandling station 6 partly to rotate, can load the turned moulding on asuccessive template already loaded with thermoformed products 2, notturned, and thus the turned products 2 are pre-stacked (see FIG. 4a),which enables the number of cycles in the time unit to be increased.

[0045] In the embodiment of a plant according to the present inventionshown in FIG. 12 there is shown a linear conveyer 50 for templates 51,e.g. of the type having an upper forward run and a lower return run anda step drive motor 52.

[0046] At a position upstream of the upper forward run there is provideda receiving station 3, where the thermoformed products 2 are loaded bythe pick up plate 30 in the template 51 which at that moment is waitingin the receiving station 3. In an intermediate position downstream ofthe receiving station, there is provided a rotating station arranged tocause every other template 51 to rotate through a predetermined angle,such a rotation being carried out by a handling device 17, e.g. onesimilar to that shown in FIG. 4. At the end of the upper forward runthere is provided a stacking station 4, e.g. a stacking station as thatdescribed with ref. to FIG. 4, where the thermoformed products 2 arestacked alternately turned to obtain stacks 7 as illustrated in FIGS. 6to 9.

[0047]FIG. 13 shows a variant of the plant of FIG. 12, in which thehandling device is a robot structure 60, which carries out the rotationof a moulding of thermoformed products 2 transported on a templateconveyer 50 and can also carry out, upon control of a control unit 25,the picking up of sample mouldings of products 2 to transfer them, forexample onto a template 71 on a second conveyer 70 nearby, in order tobe tested or transferred to a second handling or stacking line.

[0048] To this end, the robot 60 can have a telescopic arm 15, that canoscillate around a horizontal axis and turn around a vertical axis.Additionally, the robot 60 can move, e.g. in a parallel fashion to theconveyer 50, for example to position a moulding of thermoformed products2 on the conveyer 50 in a different position to that of the picking up,owing to a reversible drive motor 61, e.g. through a gear unit, causes adrive screw 62 to rotate, which engages in a nut screw 63 secured to, orintegral with, the base 64 of the robot. Advantageously, the base 64 canslide along straight guides 65 which extend parallel to the controlscrew 62.

[0049] The above described plant is subject to numerous modificationsand variations with the scope of the claims.

[0050] For example, in the embodiment illustrated in FIG. 10, thepartial rotation movement of the templates 9 a-12 a can also be directlyderived from the motion of rotation of the conveyer 5 by using asuitable transmission system.

[0051] The disclosure in the Italian patent application no.VR2001A00016filed on Feb. 15, 2001 from which priority is claimed is incorporatedherein by reference.

[0052] Any reference sign following technical features in any claim hasbeen provided to increase intelligibility of the claim and shall not beconstrued as limiting the scope of the claim.

1. A process for handling and stacking a plurality of thermoformedcontainers or lids, which comprises the following sequence of phases:obtaining during a thermoforming phase mouldings of lids and containers,having at least three stacking protrusions or spacers, all having thesame space arrangement in all the thermoformed products of the samemoulding, at least one of the stacking protrusions or spacers of a samethermoformed object being set out in a non specular symmetric way withrespect to at least a centre line of the respective container or lid andat a distance from the same centre line of the respective container orlid different from that of the others, arranging one or a moulding ofsaid containers or lids in at least one support template to keep them inorder according to the spatial arrangement that they had during thethermoforming phase, turning through a predetermined angle every otherobject or moulding of objects either containers or lids before or duringtheir transfer to a stacking station, and stacking mouldings ofthermoformed containers or lids with alternate mouldings turned throughsaid predetermined angle, so as to obtain stacks of containers or lids,where the stacking protrusions of a container or lid are offset withrespect to those of the next container or lid in each stack.
 2. Aprocess according to claim 1, wherein the said rotation phase includespicking up a moulding of thermoformed objects from a supportingtemplate, turning the said moulding or the single containers or lids ofsaid moulding, while the said thermoformed objects are lifted, andplacing the said thermoformed objects rotated through the saidpredetermined angle on the same template or on another template loadedwith thermoformed objects that have not been turned.
 3. A processaccording to claim 1, wherein the said containers or lids are rotatedthrough an angle of 180°.
 4. A plant for handling and stackingthermoformed containers or lids having at least three projections (8 a,8 b) acting as stacking spacers, at least one of which is arranged atnon specular symmetry with respect to at least a centre line (m-m) ofthe respective container or lid (2), said plant (1) including, insequence, a receiving station (3) for a container or lid or a mouldingof containers or lids (2), at least a stacking or working station (6)for said containers or lid (2), a stacking station (4) for saidcontainers or lids (2), means (5, 50) of transferring the containers orlids (2) from the receiving station (3) to the stacking station (4)through each working or handling station (6), and is characterized inthat at least one of the said handling stations (6) includes handlingmeans (17) arranged to rotate through a predetermined angle every othermoulding of containers or lids (2) before or during their transfer tosaid stacking station (4), thereby obtaining stacks (7) of lids orcontainers (2), where the stacking spacers (8 a, 8 b) of a container orlid (2) are angularly offset with respect to those of the next containeror lid.
 5. A plant according to claim 4, wherein said handling means arecomprises a support structure (15, 16) and a head or unit (17) forpicking up samples of a moulding of thermoformed products (2), which isrotatably supported rotatably and can be lift and lowered on saidsupport structure (15, 16).
 6. A plant according to claim 5, whereinsaid picking up unit (17) comprises a support member (19) rotatablymounted around a vertical axis on said support structure (15, 16), amultiplicity of spacers (20) carried by said support member (19) andextending downwards, and a holding means (21) carried by each saidspacer (20) and spaced apart with respect to the remaining holding means(21) according to the configuration of a moulding of thermoformedproducts (2) transported by said transfer means (5, 50).
 7. A plantaccording to claim 6, wherein said holding means (21) includes suckers.8. A plant according to claim 6, including a geared motor unit (18) forcontrolled rotation of said support member (19).
 9. A plant according toclaim 6, wherein said support structure includes a fixed support (16),an overhanging arm (15) having one end thereof slidably mounted along atleast a vertical guide (16 a) on said fixed support (16), and drivemeans (16 b, 16 c) to cause said overhanging arm controllably to liftand lower.
 10. A plant according to claim 6, wherein said handling meansincludes a robot (60) having at least an overhanging arm (15) mountedfor rotation either around a horizontal axis to carry outraising—lowering movements for said support member (19) or around avertical axis to transfer mouldings of thermoformed products (2) awayfrom said transfer means (5,50).
 11. A plant according to claim 10,wherein said robot comprises drive means (62) and guide means (65) tocarry out movements from and to said handling station (6).
 12. A plantaccording to claim 4, wherein said handling means include at least asupport template (9 a-12 a) for a moulding of thermoformed objects (2),a support frame (39-42) carried by said transfer means (5,50) for eachsupport template (9 a-12 a) and having a circular opening at which arespective template (9 a-12 a) is rotatably mounted, and drive means forcausing said template (9 a-12 a) controllably to rotate upon control.13. A plant according to claim 4, wherein said transfer means comprisesat least one rotating conveyor (5) with a plurality of arms (9-12). 14.A plant according to claim 4wherein said transfer means comprises atleast one linear conveyer (50).
 15. A plant according to claim 13,comprising a single station thermoforming press(31) with cut and formmould (32) having a suction plate (30) for picking up thermoformedobjects (2) thermoformed therein and arranged to discharge mouldings ofthermoformed products (2) at said receiving station (3).